Elastic yarns, with their excellent elastic and stretching properties, have been extensively used in the application fields of stretching clothes, such as leg wears, inner wears, sporting wears, etc., as well as the application fields of industrial materials.
With reference to such elastic yarns, among others, there have strongly been demanded the elastic polyurethane yarns which are capable of exhibiting high tenacity and high elongation, high recoverability, intensified chemical resistance, advanced heat resistance, etc. In recent years, especially, intensified chemical resistance is strongly desired and needed for such elastic polyurethane yarns, in cases where they are used as a mixed woven or knitted fabrics in combination with polyester yarns, and there is demanded intensified chemical resistance enough to resist caustic treatment and opal treatment of polyester yarns, namely, the resistance to alkalis, unsaturated fatty acids, quaternary ammonium salts, etc.
As the prior art taking aim to impart the intensified chemical resistance, for example, there has been known the technology which comprises allowing polyvinylidene fluoride to coexist through incorporation in a spinning solution of polyurethanes (refer to the Official Gazette of JP No. 2000-73233 A).
The elastic polyurethane yarns having polyvinylidene fluoride incorporated therein are found to show inadequate recoverability and heat resistance, and find in some instances restricted utilization in the application fields of mixed woven fabrics with polyester yarns where caustic treatment and high-temperature dyeing are required, since they still elicit merely an unsatisfactory level of chemical resistance.